It is known to provide a burner with two tangential counter-rotation air injectors disposed in a portion of a cylindrical burner chamber to produce air turbulence therein to obtain a rapid mixture of air and gas, more particularly natural gas. In such burners the gas is injected upstream of the tangential air ports by a ring of gas ports formed about the cylindrical burner housing. Such burners operate at low pressure and provide the advantage in that it produces a flame which is very intense due to the fact that the mixture of gas and air is very homogeneous because of the turbulence caused by the counter-rotation air injectors. With such burners it is possible to obtain volumeric heat release of the order of 100 MW/m.sup.3 for the combustion chamber and to provide a burner which is very compact and inexpensive per unit of power produced.
Burners having counter-rotation air injectors have been used in various industrial applications, such as for the heating liquids, be it for submerged heating tubes or for incineration. However, such burners have disadvantages and an important one is that it produces too much nitrogen oxides in the range of 200 to 400 ppm corrected at 3% 0.sub.2. It therefore limits the application of the burner, particularly in North America where pollution emission standards are very stringent.